Method of drawing wire rope



Aug- 22, 1967 R. E. CAMPBELL ETAL 3,336,784

METHOD OF DRAWING WIRE ROPE Filed Nov. 16, 1964 United States Patent O 3,336,784 METHOD OF DRAWING WIRE ROPE Robert Edward Campbell, Kenneth `William Longbottom, and Edward A. Shipley, Doncaster, England, assignors to British Ropes Limited Filed Nov. 16, 1964, Ser. No. 411,533 Claims priority, application Great Britain, Mar. 26, 1964, 13,037/ 64 9 Claims. (Cl. 72--364) This invention relates to wire strand or wire rope.

By wire strand is meant three or more wires helically twisted together or about a centre wire.

By wire rope is meant two or more wire strands helically twisted together or around a centre core.

The invention consists in a method of treating a wire strand or Wire rope in which the strand or rope is drawn through a reducing means while applying uniform backtension thereto and subjecting the strand or rope on emerging from the reducing means and while still under tension to a heat treatment stage.

the same dlameter may be seen from the following Table 1:

TABLE 1 Strand as Strand as Conventional Dyformed Dyformed stress relieved and heat strand treated Diameter, ins 0. 5 O. 5 0.5 Steel area, sq. ins.. 0.175 0.174 0.144 Weight/ft., 1bs 0. 603 0. 598 0. 494 Breaking Load, lbs 46, 900 46, 900 38,100 0.0% Proof Load, 1bs 25, 200 39, 200 28, 000 0.1% Proof Load, lbs 36, 700 43, 500 34, 100 0.2% Proof Load, lbs 40, 800 44, 800 36, 400 Elongation to fracture:

24 g. length, percent.-. 3. 1 4. 5 4. 0 Mod. of Elasticty,

p.s.i.X105 27. 2 28. 3 2B. 9

In addition to the improvement of the above mentioned properties there is also found to be an improvement in the load relaxation behaviour of the strand as shown in the following Table 2.

Preferably the heat treatment stage comprises a heating stage followed by a cooling stage.

In the case of a steel wire strand it has been found necessary to heat the strand to a temperature of between 200 C. and 400 C. the optimum temperature being of the order of 325 C. although this varies somewhat with other processing conditions viz. speed and strand size.

The reducing stage deforms the cross-section of the strand or rope previously consisting of round wires in point contact with each other to a cross section comprising wires of intertting geometrical shapes in line surface contact with each other.

Some heat will have been generated by this reducing stage and it is only necessary therefore to supply the additional heat required to raise the strand to the desired temperature.

The degree of cooling achieved by the cooling unit should be such that the strand arrives at the capstan pulling the strand through the reducing means at such a temperature that the strand does not take a permanent set due to coiling around the capstan.

The improvement in the properties of the strand as compared with a similar strand produced without the heat treatment stage or with a conventional strand of Thus at ambient temperatures the relaxation from an initial load of of the breaking load may be less than 2% in one thousand hours while improvements are also shown in the stress relaxation properties at elevated temperatures.

The improvement in properties of the steel wire strand is of particular use in connection with the use of the strand for the pre-stressing of concrete.

In this particular application as the strand is not intended as a working strand for which the best possible wear resistance and fatigue resistance are required, the optimum drafting limits may be wire,'e.g. 4% to 80% reduction in cross sectional area in conjunction with back tension in the reduction stage in the range of 2% to 615% of the breaking load of the strand.

In the drawing, FIGURES la and lb joined at the dotdash line is a side elevation of an apparatus for carrying out the process of the invention.

A strand which may be say a 7 wire strand (6 Wires helically twisted round a centre wire) or a 19 wire strand (for example two successive layers of 9 wires each helically'twisted around a centre wire) is taken off from a pay ott reel 1 and is fed over compensating rollers 2 around a capstan Wheel 3a of a drag capstan 3.

The drag capstan pivots on a pivot 3b and the downward pressure is measured on a load cell 4 to give an indication of the back tension being applied. The strand from the capstan wheel 3a passes through a post former 5 (which acts to straighten the strand) into a reduction die mounted in a die-holder 6 and then through an induction heater 7. Coil 7 is fed by a high frequency generator, a typical unit being rated at 125 kva. using a frequency of 8 kc./sec. The length of the heating coil Varies with the speed of processing.

Immediately after passing through the heating coil the strand passes a pyrometer 8 and then through a Water cooler 9 before going round the drawing-off capstan 10'.

The strand coming off the drawing-ofi capstan 10 passes to the take-off reel 11.

Various modications may be made within the scope of the invention. Thus other methods of heating may be used such as a mule furnace.

What is claimed is:

1. A method of treating a wire strand or wire rope comprising the steps of drawing the strand or rope through a reducing means while applying a uniform back tension thereto and subjecting the strand or rope on emerging from the reducing means and while still under said back tension to a heat treatment stage.

2. A method as claimed in claim 1, in which in the case of a steel wire strand the heat treatment is effected at a temperature of 200 C.-400i C.

3. A method as claimed in claim 2, in which the heat treatment is effected at a temperature of the order of 325 C.

4. A method as claimed in claim 1, in which the heat treating stage is followed by a cooling stage.

5. A method as claimed in claim 4, in which the strand or rope is coiled after the cooling stage and the degree of cooling is such that the strand or rope does not take a permanent set when it is coiled.

6. A method as claimed in claim 1, in which the reduction in cross sectional area effected by the reducing means is in the range 4% to 8%.

7. A method as claimed in claim 1, in which the back tension is in the range 2% to 65% of the breaking load of the strand or rope.

8. A method as claimed in claim 1, in which the strand tension is in the range 2% to 65% of the breaking load or rope is straightened which said strand or rope is maintained under predetermined tension during and after being straightened.

9. A method as claimed in claim 1 in which the strand or rope comprising helically wound wires is drawn through the reducing means at a specified linear speed while applying back tension thereto to produce an initial rise in the temperature of the strand and subsequently further raising the temperature of the strand by a heat treatment stage of the order of 200 C.-400 C. while the strand is still under tension.

References Cited UNITED STATES PATENTS 1,096,866 5/1914 Schinnerling 72-286 2,057,582 10/1936 McKean et al. 72-286 3,083,817 4/1963 Campbell 72-274 3,257,792 6/1966 Joy 72-274 WILLIAM W. DYER, JR., Primary Examiner.

AUDREW R. JUHASZ, GERALD A. DOST, Examiners. 

1. A METHOD OF TREATING A WIRE STRAND OR WIRE ROPE COMPRISING THE STEPS OF DRAWING THE STRAND OR ROPE THROUGH A REDUCING MEANS WHILE APPLYING A UNIFORM BACK TENSION THERETO AND SUBJECTING THE STRAND OR ROPE ON EMERGING FROM THE REDUCING MEANS AND WHILE STILL UNDER SAID BACK TENSION TO A HEAT TREATMENT STAGE. 